Pressurized container for paint additives and method of making same

ABSTRACT

A pressurized package of paint, additives is prepared by mixing water emulsion, stabilizers and a propellant in a pressurizable container. This pressurized container is then sold to retail stores where a water borne paint composition is injected into the pressurized container and sold directly to the end user.

This is a division of application Ser. No. 09/477,238, filed Jan. 4,2000, now U.S. Pat. No. 6,135,165.

BACKGROUND

This invention relates to a method and a system to allow for thepreparation of a pressurized water borne paint formulation at the pointof retail sale to the ultimate end user.

One of the most significant developments in the field of paints andother protective coatings in the last thirty years has been the rapidgrowth and widespread acceptance of water-based paints. Since they werefirst introduced in the later forties as an interior wall finishcomposed of a water-based styrene-butadiene latex, there has been agreat increase in the sale of these paints. The paints are practicallyodorless during their application and dry rapidly.

Latex wall paints produce a low sheen or gloss finish which has goodwashability within a short period after application. In cases ofscratches, mars or dirt pick-up during this period, it is only necessaryto touch up the wall with the original paint. In some cases, however,this has become impracticable because the necessity to save some of theoriginal paint or it becomes inconvenient and time consuming to prepareand clean up the equipment such as brushes and rollers. A convenientsolution would be the availability of an aerosol can containing an exactmatch of the original paint. Unfortunately, however, prepackaged waterbased aerosols are unstable and have a short shelf life, making themimpractical as a retail product. Our invention, as described below,solves this problem.

Since the introduction of the aerosol surface coatings, major steps havebeen taken to improve the formulation of these materials. Acceptableaerosol dispensed paints must have sufficient mechanical stability towithstand the mechanical shearing forces which aerosol water based paintcompositions normally experience as they are dispensed from conventionalaerosol containers. Insufficient stability results in mechanicalshearing of polymeric components of the composition. Agglomerated bitsof the composition can clog the narrow orifices of the aerosol valveoutlet and interfere with the even disbursement of paint. Agglomeratedbits can also break away for the orifice and be delivered onto thesurface of the substrate being painted, thereby marring the paint filmthereon.

Mechanical stability of paint formulations is depended in a largemeasure upon maintaining a solution of the polymer in the aerosolizedformulation. Proper mechanical stability and low viscosity have beenachieved in solvent based systems employing hydrocarbons, alcohols andother solvents. The volatility of the solvent causes rapid thickening ofthe paint as the aerosolized composition is dispensed and applied to asubstrate. The rapid thickening of the aerosol paint during and after itis dispensed is essential to commercial solvent based paint formulationswhich must be capable of adhering to vertical surfaces without running.That property of a paint composition is referred to herein as verticalcling.

Although organic solvent based aerosol systems have been developed whichhave good mechanical stability and vertical cling properties, thesolvents employed in such systems (e.g., hydrocarbons or alcohols) areflammable, toxic and environmentally undesirable. Thus, it was deemeddesirable to develop a water based paint composition which would possessthe degree of mechanical stability necessary for it to be dispensed witha minimum of breakup from a conventional aerosol valve, while at thesame time possessing a high degree of vertical cling when thecomposition is sprayed onto a vertical substrate.

In light of the environmental hazards associated with aerosolpropellants such as the fluorocarbon propellants, it is also importantto employ a propellant which is environmentally friendly, and possessesa low degree of flammability when used as a propellant for water basedconcentrate. One such propellant is dimethyl ether, which possesses verylow flammability in aqueous systems.

Another problem with solvents in water based paint systems is that overtime they begin to react adversely with the paint formulation destroyingthe desirable properties, such as vertical cling. Accordingly, it is anobject of this invention to provide methods and a system whereby astable aerosol water based paint product can be prepared at the point ofretail sale to the person who will ultimately use the paint.

It is another object of this invention to provide an aerosol water basedpaint composition which employs an environmentally safe and acceptablepropellant, while at the same time possessing the key attributes desiredin an aerosol dispensed, water based paint, i.e., mechanical stability,the ability to provide a foam-free durable coherent film on thesubstrate to which the paint is applied, the ability of the compositionto cling to vertical surfaces without running, as well as the ability toprovide finished paint films having a wide range of gloss. Inparticular, it is an object of this invention to provide a convenientsystem whereby a consumer at the retail level can obtain an aerosol canof water borne paint composition that matches a previously purchasedpaint product.

Yet another object is to provide a system and a method of formulating anaerosol paint composition at the point of retail sale that is stable andready for immediate use by a consumer. Because the final paintformulation is prepared at the point of retail sale, the contact of thepropellant with the water borne paint formulation is significantlyminimized, thus avoiding the deleterious degradation of the paintformulation. This results in a stable product with excellent performancecharacteristics.

Although aerosol water based paints are disclosed by the patentliterature (see e.g., Page et al. U.S. Pat. Nos. 4,384,661, 4,265,797,4,250,253, and 5,071,900; Suk U.S. Pat. Nos. 4,265,797 and 4,450,253;Brouillette et al. U.S. Pat. No. 4,518,734; and Rapaport et al. U.S.Pat. No. 4,482,662), these prior art formulations require that the paintcompositions must be specifically formulated to allow them to beaerosolized. However, in our invention, unlike the dimethyl etherpropelled compositions of the prior art, we provide a method and systemfor developing a pressurized can which is capable of accepting waterbased coatings which are not manufactured specifically to beaerosolized. One advantage of our invention is that it accepts nearlyany latex paint without stability problems and prevents agglomerationand gloss loss. It also provides coatings that are environmentally safe,non-flammable and may be cleaned up easily with water.

SUMMARY

The present invention provides a method of preparing a aerosol containerof water borne paint comprising of a pressurized container having afilling opening and containing a solvent mixture of a volatilepropellant, such as dimethyl ether, stabilizers, water and an emulsion.After the selection of a waterborne formulation, for example to match apreviously applied paint, it is injected into the pressurized containerthrough the filling opening to form an aerosol container of water bornepaint. The present invention provides a method of adding the water bornepaint as a last step at the point of retail sale to a mixture ofpropellant, water, emulsion and stabilizers to allow for flexibility inchoice of latex paint used, to ensure stability and to preventagglomeration.

BRIEF DESCRIPTION OF THE DRAWING

The Invention may take form in various parts and arrangement of parts.The drawing is only for purposes of illustrating a preferred embodimentand is not to be construed as limiting the invention.

FIG. 1 shows a can filling machine and pressurized container accordingto our invention.

DETAILED DESCRIPTION

A critical aspect of this invention is the preparation of pressurizedcontainer containing paint additives that can be supplied to retailestablishments whereby, as a last step, a water borne paint formulationis added immediately prior to the purchase by the user of theaerosolized paint. A necessary component of this invention is theinclusion of a propellant, one particularly preferred propellant isdimethyl ether which has been used in water based aerosol products suchas hair sprays, perfumes, air fresheners, insecticides and spraypolishes. Dimethyl ether (DME), which is water soluble, has also beensuccessfully used in water based aerosol paints. It has been founduseful, not only as a major portion of the propellant phase essential toefficient atomization of the aerosol paint for application purpose, butalso because it provides excellent co-solvency with water. The use ofdimethyl ether as a propellant/co-solvent overcomes the foaming problemsencountered with other aerosol coating containing water. It alsoovercomes any need for aromatic hydrocarbons or halogenated hydrocarbonsin the formulations.

DME is a commercially available liquefiable gas having a boiling pointof −23° C. at one atmosphere, and is soluble in water to the extent ofabout 35% by weight at 24° C. at about 5 atmospheres of pressure.Although any commercially available DME can be used in the presentinvention, one commercial supplier of DME is DuPont®. Although DME is apreferred propellant, other propellants may be used alone or in additionto DME, for example, propane, carbon dioxide, and nitrous oxide.

In addition to the propellant ingredient, our invention requires theaddition of several other components in order to obtain the ultimatedesired coating. Preferably, a solution comprising water, an emulsion,and stabilizers are also introduced into the container preferably beforethe addition of the propellant. By adding the propellant last, thepropellant can be used to pressurize the container. Alternatively, thesolution of water, emulsion and stabilizers can be added in conjunctionwith the propellant to the-container and sealed and pressurizedaccordingly.

The emulsion agent, also referred to as a resin, applicable for thisinvention consist of those rendered water soluble by neutralization ofacidic or basic sites thereon which render the emulsion dispersible inmolecular or near molecular dimensions, resulting in a single liquid Aphase. The emulsion agent used can be polyurethane, acrylics, epoxy,styrene, butadiene and any mixture thereof although this group is notlimiting. Indeed, other resin examples include styrene acrylics,urethanes, polyesters, and silicone polymers. Water soluble emulsionsare commercially available through several different suppliers. Oneexample of a commercially available acrylic latex emulsion suitable foruse herein is one obtained from S.C. Johnson Polymer, namely Joncryl537. The addition of certain acrylic emulsions to the latex systemserves to prevent gloss loss, to prevent agglomeration and to preventstability problems with nearly any latex paint.

The stabilizers used in the invention are selected are from the groupconsisting of surfactants, plastizers, antifoam agents, alcohols, pHbuffers and mixtures thereof. In particular fluoro surfactants arepreferred, specifically FC120 manufactured by 3M. The stabilizers arenecessary to insure that the water borne paint formulation, inparticular the pH of the concentrate, will not have a corrosive effecton the container. Suitable pH buffers include ammonia, and amines suchas triethanol amine. Other suitable stabilizers include AMNP-95.

Once the pressurized container of propellant, emulsion, water andstabilizers is prepared, the product is ready for sale at the retaillevel. Immediately prior to the sale the ultimate end user selects awater borne paint formulation to be added to added to the pressurizedcontainer. Typically, the paint formulation selected is to match anexisting color or type of paint previously used. A water borne paintformulation is any water soluble paint composition, preferably latexbased paints. Other water borne paint formulations include waterreducible alkyls and water, based polyurethanes. After selection, thewater borne paint composition is injected into the pressurized containerthrough the filling opening in the container to form the aerosolcontainer of water borne paint.

In order to match exist paint colors, a tint base can be added tonon-pigmented formulations to form a tinted water borne paintformulation of choice. The choice of tint bases, colors that are used tomatch a particular paint swatch, depends upon the characteristics andcolor desired of the coating. Any pigment commonly used in paintcompositions can be employed in the present invention. Examples ofuseful pigments include titanium dioxide, carbon black, phthalocyanimes,molybdates, perlenes, flavanthrones, quinacridones, iron oxide and otherknown paint tint bases.

Product enhancers, such as thickeners, corrosion inhibitors and flowmodifiers, may be added to the composition without departing from thespirit of the disclosure for the scope of the appended claims. Totalmiscellaneous paint enhancers will generally constitute less than about5% by weight of the total aerosol can content. These are preferablyadded during the preparation of the aerosolized container of paintadditives prior to the addition of the water borne paint formulation.Thickeners are employed as an ingredient because of their markedincrease in the viscosity of the composition which prevents theoccurrence of undesirable “running” of the wet paint film when it issprayed onto a slanted or vertical surface. A wide variety of acrylicemulsion thickening agents are commercially available. One example isKings PUR 60. An example of a commercially available corrosion inhibitoris AMP-95 and example of a commercially available flow modifier is anyfluorosurfactant.

Introduction of the water borne paint formulation into the pressurizedcan is accomplished using known means, preferably using a can fillingmachine. The can filling machine can be any apparatus that is known inthe art such as a pneumatically controlled aerosol can filling machinedisclosed in U.S. Pat. No. 4,938,260 (Hirz), the teachings of which areincorporated herein by reference. FIG. 1 illustrates one embodiment ofthe can filling machine 10 having placed therein for filling pressurizedcontainer 20. The propellant and the solvent mixture can be placed inthe container to be utilized as an aerosol spray paint before the cap iscrimped thereon and the paint can be forced through a filling valve by apneumatically operated can filling machine.

The method of this invention includes adding the water borne paintformulation last to avoid agglomeration of the paint particles as aresult of prolonged exposure to the propellant. Agglomeration can occurbecause the propellant, being a solvent, softens most latex polymers,and it being present at very high concentration at the dip tube opening.For example, a mixture of dimethyl ether and water is added to astandard pressurized spray paint container along with certain acrylicemulsions and stabilizers. The water acts as a dilutent for the dimethylether, which prevents the resin agglomeration at the dip tube. The waterborne paint composition is injected into the pressurized container atthe point of retail sale, immediately prior to its ultimate use by aconsumer. Because there is only a short period of time between therelatively final addition of the water borne paint formulation and enduse of the pressurized paint composition, the deleterious side effectsof the propellant do not manifest themselves.

It should be understood that the embodiments and examples disclosedherein are presented for illustrative purposes only and that many othercombinations and articles that embody the methods, formulations andsystems will be suggested to persons skilled in the art and, therefore,the invention is to be given its broadest interpretation within theterms of the following claims:

We claim:
 1. A system for preparing an aerosolized water borne paintcomposition, comprising, a. A pressurized container comprising apropellant, stabilizers, water and an emulsion; b. water borne paintformulation without the need of additional components; and c. a canfilling machine.